Heart cell death during ischemia or hypoxia following myocardial infarct may result from an extreme lowering of the free adenine ribonucleotide content within the heart cell. Leakage of purine bases and ribosides and inorganic phosphate from the heart with infarct is well documented. Mechanisms for normal maintenance of adenine nucleotides in the heart, and the changes in maintenance patterns with adenine nucleotide depletion during ischemia or hypoxia or during restoration of the adenine nucleotides following ischemia or hypoxia have not been evaluated in a quantitative manner. The metabolic pattern for normal stabilization of the adenine nucleotide pool size and the changes in this pattern with ischemia and hypoxia will be determined by a series of N15-enrichment experiments and complementary enzymological investigations. Primary concern is focused on N-6 versus purine ring N cycling in adenine nucleotide metabolites. Measurements of the changes in N15-enrichment patterns in the adenine nucleotide metabolites involve extraction from the perfused heart tissue and perfusion media followed by primary separation using a liquid chromatograph and subsequent separation, identification and characterization for N15-enrichment using combined gas chromatography-mass spectrometry (GC/MS). These investigations should indicate specific mechanisms used to regulate the adenine nucleotide pool size within the heart and the changes which occur with infarct. This data should suggest experiments to evaluate the use of specific inhibitors which may prevent adenine nucleotide washout or compounds which might promote adenine nucleotide synthesis in the infarcted heart. Additionally, the stable isotope tracer methodology can be applied in the study of other problems in purine metabolism relating to gout and cancer biology. BIBLIOGRAPHIC REFERENCES: S. H. Bishop, "Ammonia formation and amino acid excretion by Gyrocotyle fimbriata (Cestoidea)", J. Parasitol. 61, 79-88 (1975). L. B. Barnes and S. H. Bishop, "Adenylosuccinate Lyase from human erythrocytes", Int. J. Biochem. 6, 497-503 (1975).